Diabetes mellitus is a metabolic disease involving the increase of the level of blood glucose above the range of normal subjects due to the quantitative insufficiency or functional insufficiency of insulin in bodies, so that healthy life is markedly deteriorated because of microangiopathy in kidney, retina, nerve and the like and great vessel disorders such as arteriosclerosis. Hypoglycemic agents including insulin, insulin secretion-promoting agents, insulin resistance-ameliorating agents and α-glucosidase inhibitors have been widely applied so far for clinical therapeutic methods. However, these individual hypoglycemic agents have their unique problems although their usefulness is noted. For example, the effectiveness of insulin secretion-promoting agents and insulin resistance-ameliorating agents is greatly reduced in diabetic patients with severely deteriorated insulin secretion potencies of their pancreas. In diabetic patients with prominent insulin resistance, the effectiveness of insulin and insulin secretion-promoting agents is lowered. Hyperglycemic state exists in diabetic patients after meals, between meals and during fasting, namely throughout a day, compared with normal subjects. The hyperglycemic state throughout a day should be corrected as much as possible as a whole.
However, existing hypoglycemic agents have unique characteristic features of their hypoglycemic actions and cannot suppress abnormal increase in blood glucose throughout a day. For example, large-scale trial reports tell that insulin or insulin secretion-promoting agents cannot completely normalize the pattern of blood glucose variation throughout a day during the life cycles of diabetic patients, so that insulin or insulin secretion-promoting agents cannot absolutely prevent the onset of diabetic complications.
α-Glucosidase inhibitors and nateglinide and repaglinide are now used as agents for ameliorating hyperglycemia after meals. However, the hypoglycemic actions thereof are hardly sustainable in several hours after meals. As to other hypoglycemic agents, any action to immediately lower the increase in blood glucose due to meals cannot be counted thereon. As described above, the existing hypoglycemic agents cannot completely normalize the pattern of blood glucose variation throughout a day during the life cycles of diabetic patients. At a current state, therefore, expectations exist for the development of a prophylactic and therapeutic agent of diabetes mellitus, which can overcome these problems, particularly which can normalize the pattern of blood glucose variation throughout a day, as well as a prophylactic and therapeutic agent of diabetes mellitus, which is applicable to diabetic patients for whom the existing anti-diabetic agents have only poor effects.